A reef, covered at half tide, referred to in Admiralty Sailing Directions in association with Carreg y Chad as ' two foul patches' which are 'nearly out of the track'.

Sources include:
Admiralty, 1870, Sailing Directions for the West Coast of England from Milford Haven to the Mull of Galloway including the Isle of Man, pg70

Maritime Officer, RCAHMW, August 2014.